Extrasinus Zygomatic Implants: Three YearExperience from a New Surgical Approach forPatients with Pronounced Buccal Concavities inthe Edentulous Maxillacid_130 55..61

Carlos Aparicio, MD, DDS, MSc;* Wafaa Ouazzani, DDS;† Arnau Aparicio, DDS candidate;‡

Vanessa Fortes, DDS, MSc;† Rosa Muela, DDS, MSc;† Andrés Pascual, DDS, MSc;† Maria Codesal, DDS, MSc;†

Natalia Barluenga, DDS, MSc;† Carolina Manresa, DDS, MSc;† Monica Franch, MD, DDS, MSc†

ABSTRACT

Background: The surgical protocol for zygomatic fixtures prescribes an intrasinus approach ideally maintaining the sinusmembrane intact and the implant body inside the sinus while gaining access to the zygomatic bone. In the presence of apronounced buccal concavity, the implant head has to be placed far from the alveolar crest in a palatal direction, whichresults in a bulky bridge construction.

Purpose: The aim of this study was to report on the preliminary experiences with zygomatic implants placed with anextrasinus approach in order to have the implant head emerging at or near the top of the alveolar crest.

Materials and Methods: Twenty consecutive patients with pronounced buccal concavities in the edentulous posteriormaxilla were treated with 104 regular and 36 zygomatic implants as support of fixed dental bridges. Sixteen patients weretreated bilaterally and four patients were treated unilaterally. The zygomatic implants were inserted by using an extrasinussurgical approach with the implant body passing from the alveolar crest through the buccal concavity into the zygomaticbone. This enabled placement of the implant head at or close to the alveolar crest. The patients were followed from 36 to48 months after occlusal loading with a mean follow-up of 41 months. The relation of the zygomatic implants to the crestwas measured and compared with a control group of 20 patients treated with conventional placement of zygomaticimplants.

Results: No implants were lost during the study period. No pain, discomfort, or complications related to the extrasinus pathof the zygomatic implants were recorded after the initial healing period and up to the 36th-month checkup. The zygomaticimplants emerged, on average, 3.8 mm (SD 2.6) palatal to the top of the crest compared with 11.2 mm (SD 5.3) to theconventional technique.

Conclusion: The present 3-year clinical study shows that an extrasinus approach can be utilized when placing zygomaticimplants in patients with pronounced buccal concavities in the posterior maxilla. Moreover, the technique results in anemergence of the zygomatic fixture close to the top of the crest, which is beneficial from a cleaning and patient-comfortpoint of view.

KEY WORDS: edentulous maxilla, follow-up, maxillary sinus, surgical technique, zygomatic implants

Prosthetic rehabilitation of the severely resorbed

edentulous maxilla with implants constitutes a

therapeutic challenge. The loss of bone following tooth

extraction and use of dentures often results in bone

volumes too small for placement and integration of

dental implants as well as changes of the intermaxillary

relation.1 Many different approaches using bone grafts

have been presented in the literature, and the choice of

method is dictated by the severity of the resorption and

*Private practice, Clinica Aparicio, Barcelona, Spain, and Departmentof Biomaterials, Institute for Clinical Sciences, Sahlgrenska Academy,Gothenburg University, Gothenburg, Sweden; †private practice, Clin-ica Aparicio, Barcelona, Spain; ‡Universidad Europea Madrid, Spain

Reprint requests: Dr. Carlos Aparicio, Clínica Aparicio, Mitre 72-74 b,08017 Barcelona, Spain; e-mail: carlos@clinicaaparicio.com

© 2008, Copyright the AuthorsJournal Compilation © 2008, Wiley Periodicals, Inc.

DOI 10.1111/j.1708-8208.2008.00130.x

55

its effect on facial morphology. For instance, a retrog-

natic maxilla may require a Le Fort I osteotomy and

bone grafting in order to increase bone volume for

implants and correct facial morphology,2 while onlay

and/or inlay bone grafting may be sufficient in cases of

a normal intermaxillary relation.3 Moreover, implants

have been placed simultaneously with the bone grafts or

after some time of healing, the latter approach seemingly

preferred today.4 However, bone grafting procedures

are resource demanding and require long treatment

periods. There are risks for morbidity because of har-

vesting of bone grafts, and the failure rates are higher

than in nongrafted situations.5 Moreover, the proce-

dures are made in general anesthesia, and the patient

needs to be relatively healthy. One alternative to major

bone grafting procedures is the use of zygomatic

implants, which are placed through the maxillary sinus

to be apically stabilized in the zygomatic arch.6–9 This

implant was originally used in reconstruction of maxil-

lae of patients who underwent maxillectomy, and the

indication has then been widened to involve also routine

cases.10,11 Several follow-up studies have reported high

survival rates, although soft tissue problems related to

the penetration of the intraoral mucosa and the maxil-

lary sinus also have been discussed.12–21 One drawback

with the technique is the palatal emergence of the

implant head, which often is the case, because of the

desire to maintain the implant body within the bound-

aries of the maxillary sinus. This results often in a bulky

dental bridge at the palatal aspect followed by patient

discomfort and complaints.

The present study was conducted to evaluate a new

surgical technique using an extrasinus approach when

placing zygomatic implants to obtain implant head

emergence at the center of the residual alveolar crest.

MATERIALS AND METHODS

Patients

The study group consisted of 20 consecutive patients (9

women/11 men, mean age 52 years, range 44–62 years)

in need of prosthetic rehabilitation because of missing

teeth in the maxilla and treated from October 2004 to

October 2005. All patients were healthy. Of the patients,

12 were smokers; 10 patients smoked more than 10 ciga-

rettes a day. Six patients received a diagnosis as being

bruxers.

Inclusion criteria:

• The presence of residual alveolar crest with less than

4 mm in width and height, immediately distal to the

canine pillar

• The possibility to place a minimum of three

implants per quadrant

• The presence of buccal concavities in the maxillary

sinus areas, which precluded intrasinus placement

of zygomatic fixtures with the implant head emerg-

ing within a distance of 10 mm medial from the top

of the alveolar crest

Exclusion criterion is the general and local health

conditions that prevented the use of general anesthesia

and/or intraoral surgery.

Surgical and Prosthetic Procedures

The presurgical radiographic examinations included

computed tomography scans and orthopantomograms

in all the patients (Figure 1A).

The patients were treated under general anesthesia

and with local injections of lidocain/epinephrine.

Patients were given antibiotics prior to surgery. Crestal

and posterior vestibular releasing incisions were made,

and mucoperiosteal flaps were raised to expose the

alveolar crest, the lateral wall of the maxillary sinus, and

the inferior rim of the zygomatic arch. A retractor was

used to ensure good visibility of the zygomatic bone.

The zygomatic implant site was planned by striving for

placing the implant head at or near the top of the crest,

usually in second premolar/first molar regions. More-

over, the implant body should preferably engage the

lateral bone wall of the maxillary sinus while entering

the zygomatic bone. The implant site was prepared,

drilling from the palatal crest pointing the zygomatic

arch without making a previous opening to the maxil-

lary sinus nor taking into account the sinus membrane

integrity, and followed the standard drilling steps for

zygomatic implants as described.20 As a result, the

zygoma implant enters to the crestal bone or sinus cavity

from the palate crest of the premolar/molar area, then

comes out through the lateral maxillary sinus wall close

to the sinus ground/maxillar basal bone. Then the

implant goes in an extrasinus path and sometimes

engages the lateral sinus wall. Finally, the implant head

penetrates the zygoma arch and its head appears in the

superior part of the zygomatic arch (see Figure 1, A–D).

Additional conventional implants were placed in the

56 Clinical Implant Dentistry and Related Research, Volume 12, Number 1, 2010

anterior regions and, in some cases, posterior to the

zygomatic implants (Figure 2A). In 19 patients, abut-

ments were connected to the implants together with

sterile impression copings (see Figure 2B). The wound

was closed by suturing. Impressions of both jaws and

bite registration were made immediately after surgery in

order to manufacture a provisional fixed bridge to be

connected within 24 hours (see Figure 2C). Submerged

healing was used in one patient who received cover

screws before closing the wound by suturing. The

patients were prescribed postoperative antibiotics and

analgetics. The two-stage patient was scheduled for

abutment connection 6 months later for manufacturing

of a provisional bridge.

A total of 36 zygomatic implants, machined tita-

nium surface (Nobel Biocare AB, Göteborg, Sweden) in

lengths from 35 mm to 52.5 mm were used (Table 1).

Sixteen patients received zygomatic implants bilaterally,

and four patients received zygomatic implants unilater-

ally. A total of 104 conventional implants with lengths

from 7 to 18 mm and diameters of 3.75 and 4.0 mm

(Nobel Biocare AB) were used (Table 2). The zygomatic

implants had a turned surface, while the regular

implants had an oxidized surface (TiUnite™, Nobel

Biocare AB). Straight and angulated abutments (Multi-

Unit Abutment, Nobel Biocare AB) were used in 15

patients who received screw-retained bridges. Individual

abutments were used in 5 patients with cemented

bridges. All the patients but one were provided with a

provisional fixed implant-retained bridge within the

next 24 hours to the implant placement.

Removal of sutures and checkup of occlusion were

made 10 days after surgery. The provisional bridge was

replaced by a permanent bridge 4 to 5 months after

surgery (Figure 3). Radiographs were taken after 1 and

12 months of loading. Periotest (Periotest®, Siemens

AG, Bensheim, Germany) measurements of implant sta-

bility were made when replacing the provisional bridge

at the 4th to 5th month follow-up when the provisional

constructions were replaced by a permanent ones and

once a year afterward.

Follow-Up

The patients were scheduled for checkup examinations

at the following time points:

• 10 days; suture removal, checking of occlusion

• 1 month; checking of occlusion, radiography

• 4 to 5 months; replacement of provisional bridge to

a permanent one, periotest measurements

• 12 months; radiography and Periotest (Bensheim,

Germany) measurements

The checkup examinations also included assess-

ments of oral hygiene, soft tissue health, prosthesis

stability, gold-screw loosening, and other mechanical

complications. Standardized intraoral x-rays of the

B C DA

Figure 1 A, Tomographic section showing preoperative planning of an extrasinus zygomatic implant. B, Clinical view showingpreparation of the lateral sinus wall. Note intact sinus membrane in the bottom of the preparation. C, Showing insertion of thezygomatic implant. D, Showing final seating of the implant.

Extrasinusal Zygomatic Implants 57

zygomatic implants could not be made and, conse-

quently, these implants could not be evaluated with

regard to marginal bone resorption. An implant

removed for any reason was counted as a failure, and the

implants still in function were counted as survivals.

Implants in patients who did not come to checkup

appointments were regarded as unaccounted for.

Assessment of Zygomatic Implant Placement

The distance from the hole of the central screw of the

zygomatic implant head to the center of the residual

ridge was measured with calipers to the nearest 0.1 mm.

A control sample consisting of master models of 20

patients previously treated with the intrasinus approach

was taken, and the same measurements were performed.

RESULTS

Clinical Findings

All patients attended the planned follow-up appoint-

ments. The healing period following implant surgery

was normal in all patients with some postoperative pain

and swelling that could be controlled with analgetics.

There were no signs of infection neither within the oral

cavity nor in the maxillary sinus area. Healthy mucosa

covered the extrasinus part of the zygomatic implants,

and there were no pain when palpating the area.

No implants were removed but remained stable

during the follow-up.

Implant Stability Measurements

Periotest (Siemens AG, Bensheim, Germany) measure-

ments of individual zygomatic implants showed a mean

A

B

C

Figure 2 A, Clinical view after surgical placement of twoextrasinus zygomatic and five additional implants. B,Impression copings on the implants after suturing. Note theemergence of the zygomatic implants that are close to the crest.C, A temporary, fixed prosthesis, which was delivered the dayafter surgery.

TABLE 1 Length and Number of Zygomatic ImplantsUsed in the Study

Zygomatic implantlength (mm)

Number of implantsused

40 3

42, 5 7

45 13

47, 5 7

50 5

52, 5 1

Total 36

TABLE 2 Length, Diameter, and Number of RoutineImplants Used

Routine implantlength/diameter (mm)

Number of implantsused

11.5/3.75 4

11.5/4 3

13/3.75 27

13/4 10

15/3.3 3

15/3.75 20

15/4 23

18/3.75 1

18/4 13

Total 104

58 Clinical Implant Dentistry and Related Research, Volume 12, Number 1, 2010

Periotest (PT) value of -3.6 (range -5 to 3) 24 hours

after implant insertion and -3.5 (range -5 to 3) after 4 to

5 months.

Prosthetic Findings

The mean distance from the zygomatic implant to the

central part of the residual crest was 3.8 mm (SD 2.6).

On the control group, the mean distance was 11.2 mm

(SD 5.3).

DISCUSSION

The present study reports on the three year experiences

with zygomatic implants placed with an extrasinus

approach in 20 patients with extreme buccal concavities

in the maxillary sinus areas. In addition, all patients but

one received a fixed construction within 24 hours after

surgery. After a mean follow-up of 41 months, no

implants have been removed, and no patient has shown

any unexpected tissue reactions to the zygomatic

implants. Moreover, the extrasinus technique enabled

placement of the implant head at or near the top of the

residual crest, which resulted in a more normal exten-

sion of the bridge framework. Becktor and colleagues,17

using an intrasinus approach, reported a mean distance

of 11.2 mm from the hole of the gold screw to the

nearest buccal cusp, which is the same distance as found

in a control group of the present study. This is more than

the 3.8 mm found for the extrasinus zygomatic implants

in the present study. The fact that the extrasinus

implants emerged close to the top of the crest allowed

for less bulky constructions, which not only is beneficial

from a cleaning point of view but also means a better

comfort for the patients.

The good outcome with immediate loading of the

zygomatic and conventional implants of the present

study demonstrates the possibility of shortening the

treatment period considerably. This is in line with the

experiences of other authors when using zygomatic

implants in immediate loading.22–26 In a recent study

from the present group, the outcome of immediate/

early loading was reported for 25 patients treated with

46 zygomatic and 127 conventional implants and

followed up for at least 1 year.22 No implant losses

but few other complications were experienced in this

patient group. The Periotest (Siemens AG, Bensheim,

Germany) measurements showed a similar degree of

firm stability 24 hours after placement as after 4 to 5

months. The mean PT value after implant placement

in the present study was lower (ie, higher stability)

than in a previous study from the present group using

zygomatic implants with a two-stage technique.20 It

may indicate that the extrasinus technique makes it

possible to engage more bone, that is, at the alveolar

crest and along the maxillary sinus. The PT values

from the two studies were similar after 4 to 12 months,

which indicates that healing results in increased

implant stability.

The present research group has previously

reported on the clinical outcome when using the

conventional intrasinus approach with zygomatic

implants. The results were very encouraging because

no zygomatic implants and only 1% of conventional

implants were lost during a follow-up period from 6

months up to 5 years. This is in line with the findings

from other research groups and shows that the zygo-

matic implant is a reliable alternative to other recon-

structive techniques in the posterior maxilla. For

instance, Brånemark and colleagues followed 28 con-

secutive patients with 52 zygomatic implants for at

least 5 years and reported a survival rate of 94.2%.9

Moreover, Malevez and colleagues lost none of 103

consecutive implants placed in 55 patients during a

follow-up period of 6 to 48 months.15 However, other

researchers have forwarded concerns regarding the

soft-tissue health at the mucosal penetration of the

zygomatic implants and in the maxillary sinus.16,18

Becktor and colleagues encountered in their study

severe sinusitis, which required removal of three

zygomatic implants in three patients.17 It was specu-

lated that one reason may be the lack of osseointegra-

tion in the alveolar crest, which results in a oroantral

Figure 3 Occlusal view of a final fixed bridge in a patienttreated with two extrasinus zygomatic implants. The right isemerging at the top of the crest and the left one slightly palatal.

Extrasinusal Zygomatic Implants 59

communication. Similar findings were reported by

Al-Nawas and colleagues who examined the marginal

soft-tissue conditions and peri-implant microbiotia at

20 zygomatic implants in 14 patients.16 They found

signs of soft-tissue problems in 9 of the 20 patients. It

can be speculated that the extraoral approach as used

in the present study may be beneficial from a soft-

tissue health point because, in many cases, the maxil-

lary sinus is not perforated at the level of the alveolar

crest. Moreover, the use, from the beginning, of the

definitive abutment probably benefits the desmosomal

adhesion of the soft tissue to the titanium abutment

surface. One concern with the technique may be the

long-term effect of exposed threads toward the soft

tissue at the lateral aspect of the zygomatic implants.

However, Lekholm and colleagues could not observe

any increased marginal bone loss or failure rate for

machined implants with exposed threads at implant

surgery as compared with fully submerged implants

and followed up for 5 years.27 Moreover, Petruson

examined the maxillary sinuses of 14 patients with

zygomatic implants using sinuscopy and found no

signs of adverse reactions.28 As discussed by Becktor

and colleagues, it is more likely that problems with

sinusitis are more related to oroantral communications

rather than to exposed implant threads per se17. None

of the patients of the present study have shown any

adverse sensations or reactions from the region of the

zygomatic implants. It should be stressed that the

implants of the present study had a machined surface.

Today, zygomatic implants with a roughened oxidized

surface are commercially available. To the knowledge

of the present authors, no clinical follow-up studies

have been published with surface-modified zygomatic

implants.

Success criteria for evaluated osseointegrated

implants include parameters related to the marginal

bone height during loading. With respect to zygomatic

implants, intraoral periapical radiographs could not be

used to assess marginal bone levels in a standardized

manner. This was a result of the difficulty to place an

intraoral film correctly because of the lack of palate

curvature in these patients whose residual alveolar crest

had literally disappeared and of the angulated design of

the implant head. Moreover, because the stability of the

zygomatic implants is mainly achieved by engagement

of the zygomatic arch, the importance of integration in

the residual alveolar bone is not known.

CONCLUSION

The present three year clinical study shows that an

extrasinus approach can be utilized when placing zygo-

matic implants in patients with pronounced buccal

concavities in the posterior maxilla. Moreover, the tech-

nique results in an emergence of the zygomatic fixture

close to the top of the crest, which is beneficial from a

cleaning and patient-comfort point of view.

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Extrasinusal Zygomatic Implants 61